This research application of the Washington University Mass Spectrometry Resource plans: 1) To continue to provide a wide range of low resolution GCMS, and high resolution mass spectrometry services to biomedical investigators who request this assistance. 2) To continue to provide expert technical assistance, analytical services, and interpretive advice on high precision GCMS selected ion monitoring quantitation of substrate content and stable isotope enrichment in physiological samples. 3) To provide isotope ratio mass spectrometry (IRMS) services for precise measurement of hydrogen, carbon, nitrogen, and oxygen isotopes in end products of endogenous substrate metabolism occurring as a result of stable isotope tracer experiments in man. 4) To provide GC/Combusion/IRMS analyses of the highly diluted carbon isotopic enrichment values occurring in human precursor-product tracer studies to facilitate application of these studies to clinical research problems of biomedical importance. 5) To provide LCMS, CF-FAB and SCF-MS services for biochemical substrates not amenable to GCMS analysis. 6) To provide fast atom bombardment and plasma desorption ionization mass spectrometry for analysis of biopolymers of high molecular weight. 7) To make these facilities available for use by qualified investigators at the loca, regional, national and international levels.